The present invention relates to an apparatus for regulating liquid temperature (liquid thermostatic apparatus) used for keeping constant the reaction state of a sample by keeping constant the liquid temperature of the sample in a sample analyzing apparatus such as a blood analyzing apparatus.
In a sample analyzing apparatus, in order to always keep constant the progressive state of the reaction of the sample, the temperature of the liquid such as a reagent used in the reaction is kept constant by an apparatus for regulating liquid temperature. Such an apparatus for regulating liquid temperature comprises a main body having a space for passing or collecting therein liquid, a heat source such as a heater mounted on the main body, a sensor for detecting the temperature, and a temperature control circuit for operating the heat source as specified so as to keep the temperature of the main body constant according to the signal from the sensor. The reagent liquid contact with the main body inside, and heat is transmitted, so that the temperature may be kept constant.
Required conditions for the main body of such an apparatus for regulating liquid temperature are heat conductivity and chemical resistance. If the heat conductivity is poor, the liquid cannot be heated promptly, besides, the reagent contains acids and other chemicals, and it is important that the main body is not attacked by such reagent or does not degenerate the reagent.
As the materials of the main body, (a) stainless steel and (b) Pesin-coated aluminum have been used, among others.
The stainless steel is excellent in chemical resistance, but is not so good in heat conductivity (about 1/10 that of aluminum).
On the other hand, aluminum has an excellent heat conductivity of 0.56 [cal/cm.multidot.sec.multidot..degree.C.] at 20.degree. C., but is poor in chemical resistance, and it must be used by coating it with fluoroplastics or other resins excellent in chemical resistance in the area contacting with liquid. To prevent pinholes, however, the thickness of the coating must be increased. The resin is POOP in thermal conductivity, and when the coating becomes thick, an adiabatic effect is caused in the area, and the thermal conductivity becomes inferior between the main body and the liquid.